Aer Lingus is to warn that any delay in removing the Dublin Airport passenger cap could result in "very significant capacity cuts" next year.
The chief executive of the airline, Lynne Embleton, will also tell the Oireachtas Transport Committee that a reinstatement of the restriction "could cause an increase in airfares".
In her opening address to TDs and Senators, to be delivered later this morning, the Aer Lingus boss describes the passenger cap as "a historic anachronism that needs to be urgently removed".
The committee is holding a series of hearings as part of the pre-legislative scrutiny of the Dublin Airport (Passenger Capacity) Bill 2026.
Last month, the Cabinet approved draft legislation to lift Dublin Airport's 32 million passenger cap, which was a condition in a 2007 planning permission.
The restriction has been suspended by the High Court pending the outcome of legal proceedings referred to the Court of Justice of the European Union.
As a result, a record 36.4 million passengers passed through the two terminal buildings at Dublin Airport last year.
Ms Embleton says if the passenger cap was actually enforced, it would require a reduction of approximately 4.4 million passengers at the airport, which equates to over 12% of the current traffic levels.
"That would have a catastrophic impact on connectivity, on the airport, and on the wider Irish economy."
"Enforcement of the cap would also impact supply and demand dynamics and could cause an increase in airfares."
She says any enforcement of the cap "would cause serious economic harm" and that "legislative intervention is justified" in the public interest.
According to Ms Embleton, "swift enactment and decisive use of the powers in the Bill will provide certainty and stability".
However, the Aer Lingus CEO is warning that any delay to implementing the legislation "materially increases the risk of enforced capacity reductions".
"While the general scheme provides the Minister with the power to revoke or amend the planning condition, that power only takes effect once the legislation is enacted and commenced and a Ministerial order is actually issued."
Ms Embleton says severe cuts on seat capacity at Dublin Airport by the Irish Aviation Authority have been avoided only because of the legal proceedings initiated by airlines and the resulting stay imposed by the High Court, while the issue was referred to Europe.
Given that a judgment is expected from the European Court of Justice within months, she says "the duration of the current stay is therefore uncertain".
The Aer Lingus boss will tell the committee members that if the stay were to be lifted and the passenger cap remains in place when the IAA makes its capacity declaration for the Summer 2027 season, which would be due in early October, then there is "a real risk of very significant capacity cuts".
"We therefore strongly emphasise to the committee the importance of early enactment and commencement, the urgent completion of any required environmental assessment, and the inclusion of clear, specified timelines throughout the process so that the Minister can make the required order as quickly as possible".
Aer Lingus is among a number of carriers and airline representative groups that will be appearing before the Transport Committee in Leinster House today, including Airlines for America and the International Air Transport Association.
Ryanair is to warn that if the passenger cap is reinstated at Dublin Airport it would result in "fewer flights" and "higher fares".
The chief executive of the airline, Eddie Wilson, is to tell the TDs and Senators that it believes the 2007 restriction is "unlawful" and "contrary to EU US Open Skies Agreement".
In a presentation, to be made to the committee, Ryanair describes excessive noise claims from residents living in the vicinity of Dublin Airport as "bogus".
Mr Wilson says people that live near the airport, branded by the airline as "nimbys", cannot block national growth.
He says if the cap is not abolished and the number of passengers passing through the airport has to be cut back to 32 million, Ireland will lose out on new Ryanair aircraft and routes to the UK and other EU states.
